Sleep oxygen drops in dreams are related to changes in the memory brain

According to new research, hypoxia during REM sleep damages memory centers in the brain. This finding explains why many patients with sleep apnea experience cognitive problems as they age.

A new study published in the Journal of Medical Neurology on May 7, 2025 shows that when oxygen levels drop during sleep in dreams, it damages the brain circuits we need to form and retain memory. The researchers found that these oxygen droplets predict increased damage to small blood vessels and contract in key memory structures.

What makes this particularly worrying is that sleep apnea becomes more common as you age. Many people don’t know that silently put their brain health at night.

What has the research found

“Obstructive sleep apnea is a sleep disorder that increases with age, and lower oxygen levels during sleep can impair our brain and body’s ability to function properly,” said study author Bryce A. Mander, Ph.D., a study author at the University of California, Irving. “Our study found that low oxygen levels for obstructive sleep apnea, especially during REM sleep, may be associated with decreased cognition due to damage to small blood vessels in the brain and the downstream effects of this damage on memory-related parts of the brain.”

Sleep apnea occurs when the throat muscles relax during sleep, blocking the airway and forcing a person to breathe again. These breathing pauses can occur dozens or even hundreds of times a night, usually no one knows them.

The team studied 37 elderly people with an average age of 73 years, who had no cognitive problems and were not taking sleep medications. After an overnight sleep study, they found that 24 participants suffered from obstructive sleep apnea.

Using brain scans, the researchers found something compelling: The lower the oxygen levels that are reduced during REM sleep, the more damage occurs in the brain’s white matter. This damage is shown as a highlight called white matter superintensity, which is believed to reflect damage to small blood vessels in the brain.

Key findings about sleep apnea and brain health

Research reveals several important links:

• Lowering oxygen levels during REM sleep predicts more white matter damage in the brain
• Two measurements strongly predict brain damage: how low does the worst oxygen level drop at its worst and below 90% of blood oxygen in total time (doctors believe that below 90% of oxygen has attracted attention)
• People with greater vascular damage show thinning of hippocampus and endolin cortex – both are essential for memory
• Those with thinner entorhinal cortex performed poorly on memory tests that measured how well they kept information after sleeping

“To sum up, our findings may partly explain how obstructive sleep apnea leads to cognitive declines associated with aging and Alzheimer’s disease by supporting degeneration of brain regions that support memory consolidation during sleep,” Mander said.

Why REM sleep is so important

This study highlights the problems during REM sleep particularly – when most dreams occur. This sleep phase is not just about dreaming. When our brain processes emotional experiences and enhances important memories.

When oxygen levels drop repeatedly during this critical sleep phase, it can disrupt these processes and damage the brain circuits responsible for memory.

For millions of people who yelled nor, despite having enough sleep, were told to stop breathing during sleep, and these findings provide another reason to talk to a doctor. Standard treatments like CPAP machines may not only improve sleep—they can help protect brain health.

What does this mean for aging adults

While the study did not demonstrate that sleep apnea leads to brain degeneration – only showing that they are connected, it adds increasing evidence that breathing from sleep breathing can lead to cognitive decline.

The researchers noted that their study consisted primarily of white and Asian participants, so other populations may differ.

The study was funded by the National Institute of Aging and the American College of Sleep Medicine Foundation.

For older people who care about memory, addressing sleep quality may be as important as diet, exercise, and mental stimulation. There is growing evidence that protecting the brain not only requires paying attention to what we do when we are awake, but also ensuring that our brain receives enough oxygen during those crucial sleep times when strengthening and storing memories.

Can better breathing during sleep help prevent memory problems? Although more research is needed, these findings suggest that this is a question worth asking your doctor – especially if you have risk factors for sleep apnea, such as being overweight, thick neck, or being told to snack loudly.